Cycles: noise in dark sections
I guess the standard advice of making mesh light sources brighter and spot lamp sizes larger applies here, these would be the most "natural" ways of reducing noise[1].

If the Starmap is emitting light as an HDR, it might be a good idea to try Multiple Importance Sampling in Cycles.

But I do agree with you that one should expect a less noisy image at 3000 samples. Filmic blender actually doesn't affect Cycles contrary to popular belief.

Also, have a look at airenderer.com. It's a renderer that takes a noisy image (probably 200 samples is enough here) and gives you a more rendered result. It doesn't every type of scene well, but this looks like the type of scene this was built for.

sources: [1]blenderguru.com